A 52-year-old man from Delhi presents with recurrent episodes of acute pancreatitis over the past 6 months. He denies alcohol use. Physical examination reveals eruptive xanthomas on his buttocks and extensor surfaces. Fasting lipid panel shows: total cholesterol 850 mg/dL, triglycerides 2400 mg/dL, HDL 22 mg/dL, LDL 180 mg/dL. Serum amylase and lipase are elevated. Abdominal ultrasound shows no gallstones. What is the most likely diagnosis?